Certain treatments may call for the temporary or permanent interruption or modification of select nerve function. One exemplary treatment is renal nerve ablation, which is sometimes used to treat conditions related to congestive heart failure or hypertension. The kidneys produce a sympathetic response to congestive heart failure, which, among other effects, increases the undesired retention of water and/or sodium. Ablating some of the nerves running to the kidneys may reduce or eliminate this sympathetic function, which may provide a corresponding reduction in the associated undesired symptoms.
Many nerves (and nervous tissue such as brain tissue), including renal nerves, run along the walls of or in close proximity to blood vessels and thus can be accessed intravascularly through the walls of the blood vessels. In some instances, it may be desirable to ablate perivascular nerves and/or tissue using ultrasonic energy. In other instances, the perivascular nerves may be ablated by other means including application of thermal, radiofrequency, laser, microwave, and other related energy sources to the target region.
Conventionally known devices include an ablation catheter having a single electrode at the distal tip, used to deliver radiofrequency (RF) energy, for example, to the target tissue. Sometimes, it is difficult to position the electrode parallel to the vessel wall to obtain an efficient lesion pattern because the ablation catheter may not be controlled to point at the desired locations accurately. Additionally, correct positioning of the electrode may require deflection and/or torquing of the ablation device to place the electrode adjacent a target location within the blood vessel. It is noted that deflection and/or torquing of such ablation devices may include a variety of challenges, for example, potential damage of vessel walls, coagulation of surrounding blood, fouling of the electrode, and so forth.